c++ 输入缓存问题 按两次enter，cin.getline()才会读入

swtch(ch = cin.get())
{
case ‘1’: //
do
{
clear;
system(“cls”);
hello();
cout << "ninput name : ";
cin.getline(Temp.Full_name, 30);
clear;
}
while (!is_blank(Temp.Full_name));

		        do {
			         //cin.ignore();
					system("cls");
					hello();
			         cout << "ntitle : ";
			         cin.getline(Temp.title, 30);
					 clear;
		            } 
				while (!is_blank(Temp.title));

}

为什么输入名字后需要按两下enter 键 才会写入，